all: cleanup the APIs for initializing genesis (#25473)

* all: polish tests

* core: apply feedback from Guillaume

* core: fix comment

eth/gasprice/gasprice_test.go

@@ -130,10 +130,8 @@ func newTestBackend(t *testing.T, londonBlock *big.Int, pending bool) *testBacke
 	config.TerminalTotalDifficulty = common.Big0
 	engine := ethash.NewFaker()
 	db := rawdb.NewMemoryDatabase()
-	genesis, err := gspec.Commit(db)
-	if err != nil {
-		t.Fatal(err)
-	}
+	genesis := gspec.MustCommit(db)
+
 	// Generate testing blocks
 	blocks, _ := core.GenerateChain(gspec.Config, genesis, engine, db, testHead+1, func(i int, b *core.BlockGen) {
 		b.SetCoinbase(common.Address{1})
@@ -163,7 +161,7 @@ func newTestBackend(t *testing.T, londonBlock *big.Int, pending bool) *testBacke
 	})
 	// Construct testing chain
 	diskdb := rawdb.NewMemoryDatabase()
-	gspec.Commit(diskdb)
+	gspec.MustCommit(diskdb)
 	chain, err := core.NewBlockChain(diskdb, &core.CacheConfig{TrieCleanNoPrefetch: true}, gspec.Config, engine, vm.Config{}, nil, nil)
 	if err != nil {
 		t.Fatalf("Failed to create local chain, %v", err)